Nigerian women living in Kenya press for the release of Nigerian school girls kidnapped in northern Nigeria by members of the Boko Haram. / Tony Karumba, AFP/Getty Images

by Ray Locker, USA TODAY

by Ray Locker, USA TODAY

WASHINGTON - Eighty U.S. troops have deployed to the Central African nation of Chad to assist forces in the international search for the almost 300 Nigerian schoolgirls kidnapped by the Islamist radical group Boko Haram, President Obama said Wednesday in a letter to House Speaker John Boehner.

"These personnel will support the operation of intelligence, surveillance and reconnaissance aircraft for missions over northern Nigeria and the surrounding area," the letter said. "The force will remain in Chad until its support in resolving the kidnapping situation is no longer required."

Chad is on Nigeria's northeast border.

The schoolgirls were taken last month from a remote town in predominantly Muslim northeastern Nigeria. Boko Haram seeks to turn Nigeria, a nation of 170 million people, into an Islamic republic under sharia law. Christians make up half of Nigeria's population.

The troops are part of a widening commitment of U.S. resources in the search. The military's Global Hawk drone, which can remain airborne for more than 28 hours, and the MC-12 Liberty reconnaissance plane are also part of the U.S. effort. The troops going to Chad are part of a drone launch-and-recovery team.